RE: [PATCH] igb: shorten maximum PHC timecounter update interval

2018-10-26 Thread Keller, Jacob E 
> -Original Message-
> From: Miroslav Lichvar [mailto:mlich...@redhat.com]
> Sent: Friday, October 26, 2018 5:04 AM
> To: Richard Cochran 
> Cc: intel-wired-...@lists.osuosl.org; netdev@vger.kernel.org; Keller, Jacob E
> ; Thomas Gleixner 
> Subject: Re: [PATCH] igb: shorten maximum PHC timecounter update interval
> 
> On Fri, Oct 12, 2018 at 07:05:30AM -0700, Richard Cochran wrote:
> > On Fri, Oct 12, 2018 at 01:13:39PM +0200, Miroslav Lichvar wrote:
> > > Since commit 500462a9d ("timers: Switch to a non-cascading wheel"),
> > > scheduling of delayed work seems to be less accurate and a requested
> > > delay of 540 seconds may actually be longer than 550 seconds. Shorten
> > > the delay to 480 seconds to be sure the timecounter is updated in time.
> >
> > Good catch.  This timer wheel change will affect other, similar
> > drivers.  Guess I'll go through and adjust their timeouts, too.
> 
> I just realized that we need to fit there also any frequency
> adjustments of the PHC and system clock. The PHC can be set to run up
> to 6% faster and the system clock can be slowed down by up to 10%.
> 
> Those 480 seconds in the igb driver is not short enough for that.
> Should I fix and resend this patch, or send a new one?
> 
> Other drivers may have a similar problem.
> 

Hmm, good point. I'd send a v2 of this patch, unless it's already been applied 
to net or net-next.

Thanks,
Jake

> --
> Miroslav Lichvar

Re: [PATCH] igb: shorten maximum PHC timecounter update interval

2018-10-26 Thread Miroslav Lichvar 
On Fri, Oct 12, 2018 at 07:05:30AM -0700, Richard Cochran wrote:
> On Fri, Oct 12, 2018 at 01:13:39PM +0200, Miroslav Lichvar wrote:
> > Since commit 500462a9d ("timers: Switch to a non-cascading wheel"),
> > scheduling of delayed work seems to be less accurate and a requested
> > delay of 540 seconds may actually be longer than 550 seconds. Shorten
> > the delay to 480 seconds to be sure the timecounter is updated in time.
> 
> Good catch.  This timer wheel change will affect other, similar
> drivers.  Guess I'll go through and adjust their timeouts, too.

I just realized that we need to fit there also any frequency
adjustments of the PHC and system clock. The PHC can be set to run up
to 6% faster and the system clock can be slowed down by up to 10%.

Those 480 seconds in the igb driver is not short enough for that.
Should I fix and resend this patch, or send a new one?

Other drivers may have a similar problem.

-- 
Miroslav Lichvar

Re: [PATCH] igb: shorten maximum PHC timecounter update interval

2018-10-12 Thread Richard Cochran 
On Fri, Oct 12, 2018 at 01:13:39PM +0200, Miroslav Lichvar wrote:
> This fixes an issue with HW timestamps on 82580/I350/I354 being off by
> ~1100 seconds for few seconds every ~9 minutes.

This patch should go to the stable trees starting with v4.8.

Thanks,
Richard

Re: [PATCH] igb: shorten maximum PHC timecounter update interval

2018-10-12 Thread Richard Cochran 
On Fri, Oct 12, 2018 at 01:13:39PM +0200, Miroslav Lichvar wrote:
> Since commit 500462a9d ("timers: Switch to a non-cascading wheel"),
> scheduling of delayed work seems to be less accurate and a requested
> delay of 540 seconds may actually be longer than 550 seconds. Shorten
> the delay to 480 seconds to be sure the timecounter is updated in time.

Good catch.  This timer wheel change will affect other, similar
drivers.  Guess I'll go through and adjust their timeouts, too.

Thanks,
Richard